The present invention relates to a drug solution delivery device and, more particularly, a spring-loaded delivery device for delivering a drug solution into a blood vessel, extradural cavity, subcutaneous tissue, or bladder of a patient by a restoring force of a spring.
Up to now, there have been used various types of drug delivery devices as means for delivering a drug solution such as an antibiotic agent, anticancer agent or the like into a blood vessel or extradural cavity of a patient by little and little. For example, Japanese patent unexamined publication JP-A 4-2360 discloses a drug solution delivery device utilizing a contractile force of a balloon made of an elastomeric material to deliver the drug solution into a blood vessel over a relatively long period of time. The delivery device comprises a balloon having a multi-layered tubular structure made of a natural rubber and covered with an inner layer of silicone resin, a housing for holding the balloon, and flow control means for controlling a flow rate of the drug solution to be delivered to the patient. Thus, the balloon in this device serves as a container for storing a drug solution and also as a power source for delivering the drug solution.
In the device utilizing the contractile force of the balloon, however, it is inevitable for the balloon to be affected by the material used. That is, the pressure for delivery of the drug solution varies with time because of the elastomeric material used for the balloon, thus making it impossible to perform delivery of the drug solution at an accurately controlled flow rate or quantity. In addition, it is required to select an elastomeric material free from elution of ingredients as the balloon is used for storing a drug solution therein.
To solve these problems, it has been proposed to provide a delivery device of a syringe type employing an elastic member such as a helical coil spring, constant-load spring or elastic cords as means for driving the plunger, for example, in Japanese patent unexamined publication JP-A 7-509.
However, it is required to protect the device with a capsule to avoid the plunger from being accidentally pushed by hand because of the fact that the device is so designed as to push the plunger by the elastic member. Thus, the device becomes large in size and is inadequate for use in a portable form.
The present invention has been made under these circumstances and has aimed at providing a drug solution delivery device which makes it possible to fill the device with a drug solution directly from a vial as well as to observe a residual quantity of the drug solution accurately during delivery.
The present invention has been achieved on the basis of the finding that the device can be miniaturized by directly driving a gasket with driving means.
According to the present invention, there is provided a drug solution delivery device comprising: a barrel provided at a distal end thereof with a port and opened at a proximal end thereof; a gasket fluid-tightly and slidably arranged in a lumen of the barrel; a cylindrical connecting member having a proximal end and a distal end to which said gasket is being releasably connected; a plunger removably engaged with the proximal end of said connecting member; and a helical spring pressed and arranged between said gasket and said connecting member to push the gasket by a restoring force thereof to deliver a drug solution.
In case that the spring is to be pressed and arranged between the gasket and the connecting member, the connecting member may be formed into a stepped hollow cylindrical member comprising a small-sized distal portion having an external diameter smaller than an internal diameter of the barrel. In this case, the spring may be arranged so as to surround the small-sized distal portion of the connecting member. Alternatively, the gasket may be provided with a hook having an elongated shank so that the helical spring may be arranged so as to surround the shank of the hook.
In case that the distal portion of the connecting member is formed into a cylindrical form having an external diameter smaller than the internal diameter of the barrel, the spring may be mounted on the connecting member so as to surround the small-sized distal portion. In this case, the connection between the gasket and the connecting member may be released by rotating the connecting member around an axis thereof.
Further, the gasket may be connected to the connecting member by providing at least one elongated flexible hook at a proximal end thereof and removably inserting it into a circular connecting hole formed in a closure wall of a connecting member. In this case, the gasket is released from the connecting member by bending the hooks inwardly.
When employing a gasket provided at a proximal end thereof with one or more hooks having an elongated shank portion, the helical spring may be mounted on the gasket so as to surround the shank portion of the hooks. In this case, the connecting member may be provided at a distal end thereof with a closure wall having a connecting hole on an axis thereof so that the hooks of the gasket are rotatably inserted into and removably engaged with the connecting hole. The connection between the gasket and the connecting member may be released by rotating the connecting member around an axis thereof. Alternatively, the connecting member may be provided with a circular connecting hole in a distal closed-end wall thereof, while employing the gasket provided with at lease one elongated flexible hook. In this case, the connection between the gasket and the connecting member may be released by bending the hook inwardly.
The connecting member may be provided at a distal end thereof with one or two crossbars, which cross the lumen of the connecting member, for engagement with the hook, so that the connection between the gasket and the connecting member is released by turning the connecting member around an axis thereof. In this case, the connecting member may be provided at a distal portion thereof with a small-sized cylindrical portion having an external diameter smaller than the internal diameter of the barrel, and the hook is arranged in the lumen of the small-sized cylindrical portion along with a helical spring surrounding a shank of the hook.
It is preferred to disengage the plunger from the proximal end of the connecting member by rotating the plunger about an axis thereof. However, the disengagement between the plunger and connecting member is not limited to the above means. Further, it is preferred to provide plural longitudinal ribs on the inner surface of the barrel and the outer surface of the gasket in order to prevent the gasket from being rotated around an axis thereof when rotating the plunger or the connecting member. In this case, the ribs of the gasket are engaged with the ribs of the barrel so that the gasket is prevented from being rotated around an axis thereof when rotating the plunger or connecting member.
Further scope of applicability of the present invention will become apparent form the detailed description given hereinafter. However, it should be understood that the detailed description and specific example, while indicating preferred embodiments of the invention, are given by way of illustration only. Various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art form the detailed description.